Rain Water

[StrangGuy]

Hi Team,
I have been capturing rain water from my rooftop gutter down spout into a 90 gallon water reservoir. I typically wait until all the pollen and other debris has been washed away and then begin the capture.
It seems to be very good quality water. It is typically measuring 0-1 PPM on my Hanna meter. It is much purer than my city tap of 70 PPM. But I question the chemical content which may not be measureable in PPM. I have a typical shingled roof in GA. My home is about 3 years old so I don’t worry about glue too much. But what other harmful chemicals can be in the water and what is the best method to find out?
I read online that water captured from rooftops with shingles such as mine is only suitable for irrigation not drinking. I feel somewhat that if I can’t drink it then it is not good enough for my hydro plants. But then plants on farms grow under rain water so I am confused.

Thanks,
StrangGuy